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Fast charging via USB.

Discussion in 'Electronics & Electrics' started by Ratzz, May 29, 2021.

  1. Ratzz

    Ratzz Member

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    I have 4x 2.1A USB A charge ports in my custom case, supplied by a 12v 12Ah battery which is maintained by an 'always on' 12v 8A smart charger. More details are in my PC build log, among the last few posts, which is linked in my sig. (Note that the image on the link is not accurate, nor is the description. The actual item proved to be 4x 2.1A, labelled as such and tested as such by me with a Fluke multimeter and load tester. I've only tested each port individually though, I'm not sure as yet whether that is total load spread among both ports, or a valid simultaneous load per port).

    I need a new phone, as my Nokia 3.2 is shitting the bed. I can get a store credit (direct exchange does not exist due to the lack of availability of that model any more) or refund it at Big W where I bought it, as it's only 18 months into a 2 year factory warranty. I plan to use this store credit or refund towards buying a slightly better featured phone.

    I'm looking at this Vivo-Y70. One of the features that attracts me is the 'Ultra-Fast 33W Flash Charge'. It also has 128GB internal storage, a USB C connector and NFC, along with an 6.5" Amoled screen and what appears to be a competent though not exciting camera, all features which I am attracted to.

    I've no doubt that the phone will come with an appropriate fast wall wart charger, but I would prefer USB charging. My car also has a double 2.1A USB A source (although it also has a 240v source if I wanted to use the supplied fast wall wart I'm assuming it comes with, its just a little less inconvenient as the 240v socket is in the rear of the car, and the USB source is in the front).

    Can I buy, or make, a splitter of some kind which I can supply the single USB C port with double the power, such as a pair of the 2.1A charging ports? Or, even more spectacular, I calculate 33W @ 5v to equal 6.6A. Could I even use a triplet of cables into one USB C to give me 6.3A of fast charge?

    Of course the first thing anyone is going to tell me is that I should simply use the supplied charger, but anyone who follows me knows that I like to do things the hard/different way when I can.

    Humour me. Is it possible that I might be able to source or create a double or triple (charge only) USB C cable to provide the extra charge power? Or is that not the way it works?
     
    Last edited: May 29, 2021
  2. theSeekerr

    theSeekerr Member

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    That's (usually) not the way it works. There are two common high power charge schemes - USB Power Delivery (USB PD), and Qualcomm Quick Charge (QC), as well as a number of manufacturer-specific schemes.

    In general these fall into two categories:

    USB PD and QC use standard USB cables and negotiate a mutually compatible charging voltage somewhere between 4.5V and 20V. As of QC4.0, QC devices can fallback to USB PD mode when available.

    Other systems like OPPO VOOC use proprietary cables to shift more of the charging circuitry outside the phone.

    33W Vivo Flashcharge chargers appear to output up to 11V and 3A. It is unclear to me whether Flashcharge requires a proprietary cable.
     
  3. OP
    OP
    Ratzz

    Ratzz Member

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    More details on the Y70 HERE.

    It has a Qualcomm Snapdragon 665, so I assume it uses the QC FlashCharge method you've mentioned.

    The way I understand your post, a single 2.1A charging port is actually capable of delivering considerably more than that, if the phone can negotiate a larger charge with the supply and the charge port is of reasonably quality, but may or may not require a proprietary cable to do so. Is this a correct impression?

    I'll investigate whether the charger comes with a detachable USB cable rather than a hardwired cable at the wall wart end. There must be an unboxing video somewhere....

    The wall wart does has a removable USB cable rather than being hardwired, so the cable should be a suitable proprietary cable I assume?

    Cheers, thanks for your input :thumbup:. It does seem I am likely to buy one of these phones anyway, as the feature set is impressive for a $450 locally accessible phone. If I am able to get a store credit or refund, then an additional $150 will get me a substantially better phone, in terms of the feature set at least :thumbup:, at the same store I will be returning my Nokia to. The quick charge feature will certainly be nice to have, but not a dealbreaker.

    I'd be charging it exclusively by USB on my PC, or similarly in my car, so if I need the wall wart to get the quick charge, I'll just have to deal with the slower USB charge. I'm used to this, I plug my Nokia into USB anytime I am home and it's not being used anyway, so I can live with that. I assume I should be able to charge it at 2.1A from one of those high output ports though, if all else fails?

    It was just a random thought. If I could somehow draw power through 3 of those 2.1A ports simultaneously, I could charge from dead flat to a full charge in 30 minutes according to the blurb. Or less than an hour I assume if I only use a pair. Hell, it may well be a justifiable trade off to use a wall wart if it's going to be that fast, despite my preference to the contrary.
     
    Last edited: May 30, 2021
  4. _zak

    _zak Member

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    It's (annoyingly) more complex than that. If the port is USB-A, the only voltage you can get* is 5 V, and current tends to max out at 2.1, or sometimes 3 A (more than this would require thicker copper, and therefore more expensive cables). The actual current it will deliver depends on how the USB port on the power supply is set up. USB-A ports were never supposed to deliver more than 0.5 A, so to get around this (and avoid blowing up power supplies that can't deliver more than 0.5 A), every manufacturer used/uses a different method to signal the amount of current that a device can draw from that power supply. If you want more information, the answer to this Stack Exchange question provides a huge amount, though it's older (pre-USB-C). To highlight how much of a mess this all is, there are dedicated chips you can buy that go in your power supply with a USB-A port and switch between all of the various 'standards' to make your power supply able to charge as many different devices as possible.

    Since you practically can't get more than 15 W from a standard USB-A port, companies came up with new standards that allowed for higher voltages. Qualcomm's QC is probably the most well-known, but they mostly work by having the device negotiate a higher voltage and/or current from the power supply. This negotiation bit means that you can get more voltage and currnet from USB-A ports, but the power supply and device have to support the protocol. From what I've seen, most companies are starting to settle on rev 2/3 of USB PD that was released with the USB 3.1 spec, using a USB-C connector. This also requires negotiation, but can supply up to 100 W if you're using the right power supply and cable.

    One thing to note in all of this is that 11 V is not part of the USB PD standard, so whatever protocol Vivo are using, it's not USB PD. My guess is some version of Qualcomm's Quick Charge, but I can't find anything on 'Flash Charge' in terms of protocol, so it's probably best to assume that only the power supply that comes with the phone will do the fast charging. I'd be really surprised if your 4 x 2.1 A charger was able to supply more than 5 V, and even more surprised if it had the ability to negotiate with your phone. Sadly, this is where end-users are at the moment - maybe the phone supports charging at 5 V/2.1 A as well as the Flash Charge protocol, but the only way you'll find out is to plug it in and see.

    * If the power supply supports USB PD and you have the right cable and the device supports it, you can get up to 20 V. I've never seen a USB-A PD port, much less one of the cables in the wild though!
     
    Last edited: May 30, 2021
  5. power

    power Member

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    fast charge is often proprietary (like OnePlus Dash Charge) or in cases like your Nokia part of a standard like Qualcomm's Quick charge (whichever revision) and the charger and device need to be matched.

    Understanding that you need a compliant charger is half your battle - figure out what the device supports and what your charger and cables are capable of delivering.
     
  6. Sunder

    Sunder Member

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    Read up a bit on the Flash Charge standard.

    https://www.google.com/url?sa=t&sou...Vaw1qSuvqnGkehDEKrbrmTb_d&cshid=1622334283140

    It looks complex - unnecessarily so, given that USB-PD is royalty free.

    But the long and the short of it, is that it will be near impossible to trigger the phone to start drawing at the 33w rate without a professionally made charger.

    As others have said, for safety, the phone must receive some kind of signal from the charger to indicate that it is able to provide the higher current.

    Flash Charge takes it one step further - the charger is the one that constantly changes the voltage and current to protect the battery. Even if you could trigger it to accept the 33w, not having the circuitry to slow the charge rate when the battery gets hot or near full would just shorten the life of the battery, if not set it on fire.

    Not worth it mate. Stay with someone who uses an open standard.
     
  7. th3_hawk

    th3_hawk Member

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    Does fast charging actually make that much difference in the real world anyway? Or in your use case?

    My own real-world use case tends to be a phone that lasts all day that is then charged overnight. I'm still using an older charger at the bedside too so it's probably only 5W! Being an iPhone 11 Pro Max I'm sure it takes its sweet time to charge too, but I've never really stopped to think about it since it works for me.
    The car is 2.4A as are pretty much every other charger around the house, but the bedside is still that old charger chugging along :p I'm not playing intensive games that drain the battery requiring multiple charges a day to keep up... but then maybe I'm not hip and with it anymore :p

    Back when Apple first introduced this as an option on the iPhone X there was lots of discussions which largely landed on a graph showing that while fast charging was waaaay faster than the stock 5W charger, anyone using a 2.4A (12W) charger wasn't getting as much charge in at 30 minutes... but by 60 minutes things were levelling out. So unless you really really needed to slam in as much power as possible in a short amount of time, it didn't matter too much as long as you had a 2.4A USB A power supply.
    Link: https://www.macrumors.com/guide/iphone-x-fast-charging-speeds-compared/

    A more recent iPhone 12 charge article doesn't test the 12W wired option, but given they are stating the same 21% using a 5W charger I would hazard a guess the 12W still provides about the same delta.
    https://www.tomsguide.com/news/iphone-12-charging-speed-tested-20w-vs-magsafe-vs-5w

    It's times like these that I think maybe I should treat both my wife and I's phones to new chargers one of these days and upgrade the old units in the bedroom...
     
  8. Renza

    Renza Member

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    I wouldn't if you're just using it to charge your phones overnight. slower charging is better if you don't need to charge it fast, as it produces less heat and puts less stress on the battery. By all means, have a fast charger around for when you need it, but if you have the luxury of time on your hands then the old 5w charger will be beneficial in the long run.
     
    JSmithDTV likes this.
  9. mtma

    mtma Member

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    This is because USB-A doesn't have the lines needed for USB PD even on the 3.0 spec connector with the extended pinout.
     
  10. OP
    OP
    Ratzz

    Ratzz Member

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    I think I will simply connect the phone to one of the 2.1A charge ports, using the cable which comes with the phone, and see how it goes. It will just be the same routine as I've always done with my Nokia, so no biggy, I'm used to it. I was, as usual, just attempting to go with an overkill solution for a problem that doesn't exist :lol:

    It was just a brainfart, but the smell has cleared now.
    Thanks guys for your input. Much appreciated.
     
  11. _zak

    _zak Member

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    Apparently USB PD rev 1 worked by sending control signals over the VBUS line, so it's possible, if highly unusual - unusual enough that I only found out about it when I was checking what USB PD voltages were!
     

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